Method and apparatus for controlling volatile-forming constituents



Oct. 20, 1964 T. R. SCHUERGER 3,

METHOD AND APPARATUS FOR CONTROLLING VOLATILE-FORMING CONSTITUENTS Filed June 6, 1957 3 Sheets-Sheet 1 /N VE N TOR THOMAS R. SCHUERGER A ll'orney T. R. SCHUERGER METHOD AND APPARATUS Oct. 20, 1964 3,153,587

FOR CONTROLLING VOLATILE-FORMING CONSTITUENTS 5 Sheets-Sheet 3 Filed June 6, 1957 NW t E lnl H Nm R 5 fi il .3 Eat A I .8 mv S Qv mm QMEQCQ b mm 3 NV 4 wHm M/VENTOR THOMAS H. SCHUERGER Patented Oct. 20, 1964 3,153,587 METHOD AND APPARATUS FOR CQNTROLLING VULATILE-FOG CONSTITUENTS Thomas R. Schuerger, Monroeville, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed June 6, 1957, Ser. No. 664,070 26 Claims. (Cl. 75--5) This invention relates to an improved method and apparatus for controlling the content of volatile-forming constituents in sinter feed or the like.

Although my invention has general application to sintering or other procedures wherein a solid material is mixed with a combustible material and the latter is burned, it is especially applicable to controlling carbon and/or moisture content in iron oxide sinter feed. A typical iron oxide sinter feed consists essentially of ore fines, scale, flue dust, hot recycled sintered fines, and' carbonaceous fuel, such as coke or anthracite fines. As the feed is compounded, the various materials are deposited on a main conveyor from individual bins. Material discharged from the conveyor is moistened, mixed in a pug mill or the like, and fed continuously to a traveling grate sintering machine, where it is ignited and burned. During burning, carbon and moisture in the feed evolve in the flue gases as CO CO and water vapor and hence may be described generically as volatile-forming constituents.

In order for a sintering machine to operate properly and produce high quality sinter, the volatile-forming constituents must be proportioned accurately with respect to the other constituents. They can be proportioned with reasonable accuracy simply by weighing the various materials as they are brought together. Proportioning can be accomplished automatically with a belt scale which continuously weighs ore deposited on the main conveyor, weigh feeders which deposit definite weights of other solids thereon, and ratio devices which pace both the weigh feeders and the water additions in accordance with the weight registered on the belt scale. The individual devices used in effecting such proportioning are available commercially, and one suitable combination thereof is described in my co-pending application Serial No. 579,326, filed April 19, 1956 (now abandoned). A continuation-in-part of said application issued as Patent No. 2,980,291, April 18, 1961.

I have observed that the accuracy of proportions determined only by weighing the materials is disturbed by such variables as changes in the carbon content of the fuel, changes in the quantity and carbon content of flue dust, changes in relativehumidity, and changes in the initial moisture content of the materials. For example, if a carbon content of 4.0% is sought in the finished sinter feed, the actual content may vary from about 3.5 to 4.5%, an error of plus or minus 12%. The moisture content is subject to similar error. While most sintering operations can tolerate errors of this magnitude, their avoidance would be quite desirable.

An object of the present invention is toprovide an improved method and apparatus for controlling the content of volatile-forming constituents of sinter feed or the like more accurately than is possible by weighing alone.

A further object is to provide an improved method and apparatus for effecting suchcontrol in which the actual -materials going into the sinter feed.

content of volatile-forming constituents in the feed is determined accurately and automatically by continuous analysis of flue gases.

A further object is to provide an improved method and apparatus which control the content of a volatile-forming constituent in accordance with the actual weight of this constituent as determined by continuous analysis of the flue gas, rather than a weight based on an assumed analysis of the starting materials.

A more specific object is to provide an improved method and apparatus for controlling the content of volatile-forming constituents in sinter feed in which the actual content of the constituent is continuously determined by flue gas analysis, and the device regulating addition of the constituent is adjusted periodically to eliminate any difference between the measured content and the desired In accomplishing these and other objects of the invention, I have provided improved details of structure, a preferred form of which is shown in the accompanying drawings, in which:

FIGURE 1 is a diagrammatic showing of a sintering installation equipped with my control apparatus;

FIGURE 2 is a schematic showing of the means for measuring mols of flue gas embodied in my apparatus;

FIGURE 3 is a schematic showing of the means for determining the carbon content of the sinter feed embodied in my apparatus;

FIGURE 4 is a schematic showing of the means for controlling a volatile-forming constituent from an analysis based on the flue gas as embodied in my apparatus;

and

FIGURE 5 is a schematic showing of the means for determining the moisture content of sinter feed embodied in my apparatus.

FIGURE 1 shows diagrammatically a typical conventional sintering installation, which includes a main conveyor Ill for compounding sinter feed and a downdraft traveling grate sintering machine 11. A plurality of bins, four of which are illustrated and designated 12, 13, 14 and 15, are situated above conveyor 16 for supplying various In the example of an iron oxide sintering operation, bin 12 can supply ore fines, bin 13 flue dust, bin 14 carbonaceous fuel fines, and

bin 15 hot recycled sinter fines. Commonly such an installation includes additional ore bins and possibly additional fuel bins, butthese have been omitted from the showing in the interest of simplicity. Material supplied from the bins discharges from the right end of conveyor 10, as viewed in FIGURE 1, and goes to a pug mill 16 where water is added from a source 18 containing an adjustable control valve 19. After the moistened material has been thoroughly mixed in the pug milL'it passes over a conveyor belt 20 and thence is deposited as'a bed on the right end of the sintering machine 11 and ignited under an ignition hood 21. A fan 22 draws combustion air downwardly through the bed of material on the sintering machine. The resulting flue gas passes through a plenum chamber 23 beneath the bed and out a stack 24, the fan 22 being situated between the chamber and stack Finished sinter discharges 'from the left end of the machine. 7

In accordance with known practice, bin 12 is equipped with a table feeder 25, bins 13 and 14 with weigh feeders 26 and 27 respectively, bin 15 witha table feeder 28,

and conveyor with a belt scale 29. Table feeder 25 is adjusted manually to deposit approximately a desired quantity of ore on conveyor It), and the belt scale 29 continuously determines the true quantity deposited. The belt scale is connected to the weigh feeders 26 and 27 and the water valve 19 through ratio devices 34 31 and 32 respectively. The ratio device 30 is adjusted manually to pace the weigh feeder 26 so that it adds material (flue dust in the example) in any desired ratio to the weight of ore registered by the belt scale. The ratio devices 31 and 32 are adjusted through means constructed in accordance with my invention and hereinafter described so that they pace the weigh feeder 2'7 and regulate valve 19 to add volatile-forming constituents (fuel and water in the example) in a desired ratio to the weight of ore. The table feeder 28 is adjusted to feed recycled sinter fines substantially at the rate received, except that surge capacity of bin allows the feed rate to remain constant for extended periods. In sintering iron oxide, hot recycle fines are equivalent to ore, and my aforementioned patent describes a method and apparatus for automatically taking their weight into account in operating the ratio devices. Preferably the same method and apparatus are included when the present invention is practiced; otherwise an arbitrary adjustment can be made in the ratio devices to compensate for recycled material added to the conveyor beyond the belt scale 29.

The weigh feeders, belt scale and ratio devices per so are known and available commercially. A weigh feeder includes essentially a conventional table feeder, a belt conveyor which receives material from the table feeder and delivers it to the main conveyor 10, a belt scale which weighs material on the belt conveyor, and a suitable controller for pacing the table feeder in accordance with this weight. The ratio device 39' or 31 acts on the controller to provide the proper adjustment. Reference can be made to my aforesaid co-pending application for a more complete diagrammatic showing of a weigh feeder. An example of a suitable belt scale is shown in Frazel Patent No. 2,664,286, and examples of suitable ratio devices in Donaldson Patent No. 2,304,783 and Sorteberg Patent No. 2,643,055. These particular devices are pneumatically operated and the connections between them are air conduits, but it is apparent equivalent electronic devices can be substituted.

In practicing the present invention, the quantities of controlled volatile-forming constituents actually present in the, sinter feed are determined by continuous analysis of the flue gas." Automatic means represented by a block 33 in FIGURE 1 are connected to the plenum chamber 23 for continuously measuring the number of mols of flue gas passing therethrough. In the present example wherein carbon and moisture are controlled, additional automatic means represented by blocks 34, 25 and 337 are connected to this chamber for continuously analyzing the flue gas for its content by Volume of CO C0 and H 0 respectively. The individual devices embodied in the foregoing means, as well as the computer components and recorders which they operate, are available commercially and not of my invention; hence they are not shown in detail. Nevertheless examples of suitable devices for the purpose are identified hereinafter, and the way in which they can be assembled is fully explained.

The means 33 for measuring total mols of fine gas'and the means 34 and 35 for analyzing it for CO and CO transmit signals to a carbon computing means represented by a block .38 in FIGURE 1. A belt scale 39 on conveyor also transmits a signal to this computing means proportionate to the total weight of feed, including moisture addedat: the water source 18. From these signals the computing means continuously determines the actual carbon content of the sinter feed, and itself transmits a signal proportionate thereto. This latter signal goes to acarbon control computing meansrepresented by a block 40 and to a carbon indicator 41. A manually adjustable carbon setting device 42 also transmits a signal to the control computing means 41 proportionate to the carbon content desired in the sinter mix. The control computing means 40 transmits a signal to the ratio device 31, which signal periodically adjusts this device to the correct setting needed to deposit the desired quantity of fuel on the main conveyor 10. The indicator 41 continuously shows the actual carbon content of the sinter feed.

The means 33 for measuring total mols of line gas, the means 37 for analyzing it for moisture and the belt scale 39, transmit signals to a moisture computing means represented by a block 45 in FIGURE 1. An analyzer 46, which continuously determines moisture content in the combustion air, and a setting device 47, which is adjusted manually in accordance with the chemically fixed moisture content of the materials going into the feed, also transmit signals to the moisture computing means 45. From these signals. the computing means continuously determines the content of the moisture in the sinter feed actually derived from additions at the water source 18, and itself transmits a signal proportionate thereto. This signal goes to a moisture control computing means represented by a block 48 and to a moisture indicator A manually adjustable moisture setting device 5d also transmits a signal to the control computing means 43 proportionate to the desired free moisture content in the sinter feed. The control computing means 48 transmits a signal to the ratio device 32, which signal periodically adjusts this device to the correct setting needed to add the desired quantity of moisture to the sinter feed before it enters the pug mill 6. The indicator 4? continuously shows the active free moisture content of the sinter feed.

Means for Measuring Mols of Flue Gas FIGURE 2 shows schematically one example of a suitable means 33 for continuously measuring the volume or number of mols of flue gas passing through the plenum chamber 23. In this example the number of mols are determined by automatically and continuously solving the equation:

MM N K T wherein N represents the molar flow rate p1 represents the upstream pressure above a constriction or orifice through which the gas flows,

p2 represents the downstream pressure,

T represents the absolute temperatureof the gas, and

K represents the calibration constant for the constriction.

A constriction through which the gases flow is indicated schematically at 53. A suitable device for measuring both pl and p2 is the transducer and associated circuit shown in Carlson Patent No. 2,059,549. A transducer 54 is located on the upstream side of constriction 53 and measures p1, and another transducer 55 is located on the downstream side and measures p2. As shown in Carlsons FIGURE 5, the pressure can control the posi tion of a sliding contact 36, similarly identified in my own FIGURE 2. Any conventional thermocouple 56 can be used to measure T and is connected to a conventional automatic recorder 57, having a pointer indicated schematically at 58.

The pointers 36 operated by the transducers 54 and 55 are mechanically linked to the movable pointers of conventional slide wire potentiometers 59 and 6t) respectively. These potentiometers are connected to any suitable voltage source and thus transmit voltages proportionate to p1 and )2 respectively. These voltages go to a computer 53 which'continuously subtracts the second voltage from the first, and thus transmits a voltage proportionate to the algebraic sum (pl-p2). An example of a suitable computer 63 is available from George A. Philbrick Researchers, Incorporated, 230 Congress Street, Boston, Massachusetts and is identified as the D3-A Adding Component in their publication Catalog and Manual on GAP/ R High Speed All-Electronic Analog Computers for Research and Design, copyright 1951. The output voltages from potentiometer 59 and computer 63 go to a computer 64- which continuously multiplies the two voltages and thus transmits a voltage proportionate to the product p1(p1-p2). An example of a suitable computer 64 is available from the same supplier and is identified as the K t-MU Multiplying Component in the same publication. 7

The pointer 58 of the temperature recorder 57 is mechanically linked to the movable pointer of another conventional slide wire potentiometer 65, which is connected to any suitable voltage source and thus transmits a voltage proportionate to T. The output voltages from computer 64 and potentiometer 65 go to a computer 66 which continuously divides the first by the second and thus transmits a voltage proportionate to the quotient An example of a suitable computer 66 is the same as that used for computer 64, as explained in the same publication. The voltage from computer 66 goes to a computer 67 which continuously extracts the squareroot and multiplies the result by the constant K, and thus transmits a voltage proportionate to or N, which is the number of mols of line gas. An example of a suitable computer 67 is available from the aforementioned supplier and is identified as the K3-T Square Root Component in the same publication. The output voltage from computer 67 is used in boththe carbon and moisture computing means 38 and 45, as hereinafter explained.

Carbon Computing Means FIGURE 3 showsschematically one example of suitable means 34 and 35 for analyzing the flue gas for its content by volume of CO and C0 and of a carbon computing means 38. The carbon content of the sinter feed is determined by automatically and continuously solving the equation:

wherein C represents the weight fraction of carbon,

N represents the total mols of flue gas,

g represents the CO content in the flue gas by volume,

It represents the CO content in the flue gas by volume, and

M represents the weight of sinter feed, including added moisture.

In practice carbon in sinter feed burns almost completely to CO hence omission of means for analyzing flue gases for CO would not cause significant error. It should also be pointed out that the fractions by volume of CO and CO can be added directly in computing carbon, since a "volatile-forming control computing means suitable for 6 absorbing gas such as nitrogen and pure gas to be determined by the analysis, in this instance C0 The infrared source casts its rays through the first chamber and thence the two parallel chambers and acts on a differential thermopile, which produces a voltage proportionate to the radiation absorbed by the sample, the absorbed radiation being proportionate to the fraction by volume of C0 The recorder 71 can be of any conventional construction having a movable pointer 72. The means 35 for analyzing flue gas for CO similarly includes an analyzer 73, and a recorder 74 which has a movable pointer 75. These devices can be identical to those used for CO analysis, except that the infrared analyzer 73 contains CO.

The carbon computing means 38 includes a pair of conventional slide wire potentiometers 76 and 77 whose movable pointers are mechanically linked to the movable pointers 72 and of the recorders for CO and CO respectively. These'potentiometers are connected to any suitable voltage source and thus transmit voltages proportionate to the content of CO and CO, represented by g and h in the equation. These voltages go to a computer 78, which continuously adds them and thus transmits a voltage proportionate to the sum (g-l-h). Computer 73 can be similar to computer 63, an example of which already has been identified. The output voltage from computer 7 8 goes to a computer 79, which continuously multiplies this voltage by 12 (the atomic weight of carbon) and thus transmits a voltage proportionate to 12(g+h). An example of a suitable computer 79 is the K3C ooefificient component described in the aforementioned Philbrick publication.

Belt scale 39 is arranged to produce a voltage proportionate to the weight of sinter feed registered thereon. In the example of a scale like that shown in Frazel Patent No. 2,664,286, the direct output is a pneumatic pulse which appears in a line 17, similarly identified in my FIGURE 3. To convert this pulse to an electric signal another transducer and recorder 81 similar to that shown in Carlson Patent No. 2,059,549 can be connected to line 17 of Frazel. The movable pointer 36a of the recorder is mechanically linked to the movable pointer of a conventional slide wire potentiometer 82, which is connected to a suitable voltage source and thus transmits a voltage proportionate to the weight M in the equation.

The output voltages from computers '79 and potentiometer 82 go to a computer 83 which continuously divides the former by the latter and thus transmits a voltage proportionate to the quotient or C, which represents the carbon content of the feed.

Examples of suitable computers 53 and 84 are the same as those of computers 64 and 66, already-identified. The voltageproportionate to C goes to the carbon indicator 41, which can be any conventional recording-type meter, and to the carboncontrol computing means 44) hereinafter described.

Volatile-Forming Control Computing Means FIGURE 4 shows schematically one example of a both carbon and moisture (blocks 49 and 48 in FIGURE 1). For convenience I'describe its action in controlling carbon, but its action in controlling moisture is identical.

7 31 which paces the weigh feeder 27 is determined by solving the equation:

New setting=C'+C C wherein C represents the present setting,

C represents the desired percent carbon, and C represents the measured percent carbon.

The ratio device 31 has a movable controller 87, which in the example of the force bridge shown in Sorteberg Patent No. 2,643,053 varies force B applied to the bridge. This controller is mechanically linked to the movable pointer of a conventional slide wire potentiometer 83 which is connected to anysuitable voltage source and thus transmits a voltage proportionate to the present setting C. The carbon setting device 42 includes a conventional slide wire potentiometer which is connected to any suitable voltage source and whose pointer is set manually to any desired carbon percentage. Thus the setting device transmits a voltage proportionate to the desired percentage C The carbon computing means 38 already described transmits a voltage proportionate to the measured percent carbon C. The three voltages C, C and C go to a computer 89 which continuously adds the first and second and subtracts the third and thus transmits a voltage proportionate to C -C C, the new setting. An example of a suitable computer 89 is the same as that used for computer 63 or 78 already identified.

The carbon control computing means includes two conventional recording meters 9% and 91. The drive motor of meter 90 is connected in series with a set of normally closed contacts 92, while the motor of meter 91 is connected in series With a set of normally open contacts 93. Both sets of contacts 92 and 93 are mechanically linked to a timer 9d of any conventional construction. Periodically timer 94 briefly opens contacts 92 and closes contacts 93. The output voltage from computer 89 goes to meter 9%, which has a movable pointer 95. This pointer is mechanically linked to the movable pointer of another conventional slide wire potentiometer 96, which is connected to any suitable voltage source and thus transmits a voltage proportionate to the computed new carbon setting. This voltage goes to meter 91, but as long as contacts 93 remain open meter 91 does not act.

Meter 91 has a movable pointer 97 which is mechanically linked to the controller 87. When contacts 93 close, pointer 97 moves to a position determined by the computed new setting and thus moves controller 87 to this setting. The simultaneous opening of contacts 92 holds meter 90 at this same setting already applied from computer 39. Consequently a change in the setting of controller 87, which immediately changes the factor C, does not immediately change the position of pointer 5. Otherwise the circuit would be unstable and any change would cause indefinite hunting. When contacts again open and 92 close, pointer 95'moves to its new setting. The changed setting shohrtly changes the measured value of C to approach or conform with the desired carbon content C Timer 94- acts to change the setting of controller 37 only at intervals sufiiciently spaced that the feed whose carbon content has changed has had time to reachthe sinter bed. Thus the next opportunity for a changed setting reflects the change in C resulting from the preceding change in setting.

atmosphere for moisture content by volume, and of a moisture computing means 45. The moisture content of the sinter feed is determined by automatically and continuously solving the equation:

wherein y represents the weight fraction of moisture,

N represents the total mols of flue gas,

s represents the moisture content of the flue gas by volume,

r represents the moisture content of the atmosphere by volume,

it represents the fixed moisture content of the feed by weight, and

M represents the weight of sinter feed including added moisture.

The analyzers 3'7 and 46 can be of similar construction, and one example of a suitable analyzer is that shown in Allen et a1. Patent No. 2,359,278. An instrument similar to that shown in this patent is available commercially under the trade name Foxboro Dewcel from the Foxboro Company, Foxboro, Massachusetts, and is described in their publication Dew Point Recorders and Controllers Bulletin 11-11. These analyzers are equipped with automatic recorders which have movable pointers designated 1130 and 1tl1 in FIGURE 5. The scales along which these pointers operate are logarithmic. The pointers are mechanically linked to movable pointers of potentiometers 1m and 1% which have antilogarithmic windings. These potentiometers are connected to suitable voltage sources and thus transmit voltages linearly proportionate to the moisture content of the flue gas and the atmosphere, that is, s and r respectively.

The output voltages from potentiometers 102 and 103 go to a computer 194- which continuously subtracts the latter from the former and thus transmits a voltage proportionate to (s-r). This voltage goes to another computer 1% which continuously multiplies it by 18, the molecular weight of water, and thus transmits a voltage proportionate to 18(s-r). This last voltage and a voltage proportionate to M, the total weight of sinter feed registered on scale 39 and developed by potentiometer 82 shown in FIGURE 3, go to a computer 106, which divides the former by the latter and thus transmits a voltage proportionate to 18(s-r) Ill This voltage and a voltage proportionate to N, the total mols of flue gas from the measuring means 33 shown in FIGURE 2, go to a computer 1tl7 which multiplies them and thus transmits a voltage proportionate to which represents the moisture in the sinter feed. The computers 1%, 1G5, 1%, 107 and 1% can be similar u, ory

respectively computers as, 79, 66, as, and 63 already identified.

The output voltage proportionate to 3 goes to the moisture indicator 49 and'to the moisture control computing means 48, which is similar to that used for controlling carbon and has already been described. The control computing means 48 for moisture periodically sets the controller of the ratio device 32 in the same manner as the other sets the controller for the ratio device 31.

ln'accordance with my control method, the setting device 42 is set manually to the fraction of carbon desired in the sinter feed. The setting device 47 is set manually to the fraction of fixed moisture already in the materials as determined by analysis. The setting device 50 is set manually to the fraction of free moisture desired in the sinter feed. With the sintering apparatus in operation, the actual fraction of carbon in the sinter feed and the actual fractions of free moisture are determined continuously by analysis of the flue gases. Periodically the carbon and moisture additions are corrected so that actual fractions conform with the desired fractions.

From the foregoing description it is seen that my invention affords a fully automatic means for closely controlling the content of volatile-forming constituents in sinter feed or the like. Although the invention relies on after-the-fact analyses, it effects a considerably more accurate control than can be attained solely by Weighing the constituents. Changes in analysis of materials necessitating changes in feeding rates usually occur gradually over a period and not suddenly. Hence, when a change commences, my invention compensates with only an immaterial lag.

While I have shown and described certain preferred embodiments of my invention, it is apparent that other modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. In a sintering installation which includes means for compounding the constituents of a sinter feed, at least one of the constituents being Volatile-forming, means for burning the feed and thereby evolving said volatile-forming constituent in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the content of said volatileforming constituent comprising means connected with said passage for measuring the content of this constituent in the feed through analysis of flue gas, and means for adjusting said compounding means to bring the measured content thereof into conformity with the desired content.

2. In a sintering installation which includes means for compounding the constituents of a sinter feed, at least one of the constituents being volatile-forming, means for proportioning said volatile-forming constituent in accordance with the weight of other constituents, means for burning the feed and thereby evolving said volatileforming constituent in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the content of said volatileforming constituent comprising means connected with said passage for measuring the content of this constituent in the feed through analysis of flue gas, and means connecting said measuring means and said proportioning means to adjust the latter to bring the measured content thereof into conformity with the desired content.

3. In a sintering installation which includes means for compounding the constituents of a sinter feed, at least one of the-constituents being Volatile-forming, means for burning the feed and thereby evolving said volatileforming constituent as volatile material in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the content of said volatile-forming constituent comprising means connected with said passage for measuring the volume of flue gas, means connected with said passage for analyzing the flue gas for its content of said volatile material, means for Weighing the sinter feed, computing means operatively connected with said volume-measuring means, with said analyzing means, and with said weighing 'means for determining the content of said volatile-form" ing constituent in the sinter feed, and means for adjusting said compounding means to eliminate differences between the content of said volatile-forming constituent as determined by said computing means and the desired content thereof. I I

4. In a sintering installation which includes means for compounding the constituents of a sinter feed, at least one of the constituents being volatile-forming, means for it proportioning said volatile-forming constituent in accordance with the weight of other constituents, means for burning the feed and thereby evolving said volatile-forming constituent as volatile material in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the content of said volatile-forming constituent comprising means connected with said passages for measuring the volume of flue gas, means connected with said passages for analyzing the flue gas for its content of said Volatile material, means for weighing the sinter feed, computing means operatively connected with said volume-measuring means, with said analyzing means, and with said weighing means for determining the content of said volatile-forming constituent in the sinter feed, and means connecting said computing means and said proportioning means for adjusting the latter to eliminate differences between the content of said volatile-forming constituent as determined by said computing means and the desired content thereof.

5. In a sintering installation which includes means for compounding the constituents of a sinter feed, at least one of the constituents being "olatile-forming, means for proportioning said volatile-forming constituent in accordance with the weight of other constituents to produce a desired content of the volatile-forming constituent in the feed, means for burning the feed and thereby evolving said volatile-forming constituent as a volatile material in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the content of said volatiie-forming constituent more accurately than the control based on proportioning by Weight alone comprising means connected with said passage for measuring the content of said volatile constituent in the feed through analysis of flue gas, and means connecting said measuring means and said proportioning means for periodically adjusting the latter to eliminate any difference between the content of said volatile-forming constituent as determined by said measuring means and the desired content thereof.

6. In a sintering installation which includes means for compounding the constituents of a sinter feed, at least one of the constituents being volatile-forming, means for proportioning said volatile-forming constituent in accordance with the weight of other constituents to produce a desired content of the volatile-forming constituent in the feed, means for burning the feed and thereby evolving said volatile-forming constituent as volatile material in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the content of said volatile-forming constituent more accurately than proportioning by weight alone comprising means connected with said passage for measuring the volume of flue gas, means connected with said passage for analyzing the flue gas for its content of said volatile material, means for Weighing the sinter feed, computing means operatively connected with said volumemeasuring means, with said analyzing means, and with said Weighing means for determining the content of said volatile-forming constituent in the sinter feed, and a control computing means connected to said first named computing means and to said proportioning means for periodically adjusting the latter to eliminate any difference between the content of said volatile-forming constituent as determined by said first named computing means and the desired content thereof.

7. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being carbonaceous fuel, means for burning the feed and thereby evolving volatile oxides of carbon in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the carbon content in the feed comprising means connected with said passage for measuring the carbon content in the feed through analysis of the flue gas, and means for adjusting said compounding means to'bring ill the measured carbon content into conformity with the desired carbon content.

8. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being carbonaceous fuel, means for proportioning said carbonaceous fuel in accordance with the weight of other constituents, means for burning the feed and thereby evolving volatile oxides of carbon in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the carbon content in the feed comprising means connected with said passage for measuring the carbon content in the feed through analysis of the flue gas, and means connecting said measuring means and said proportioning means to adjust the latter to bring the measured carbon content into conformity with the desired carbon content.

9. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being carbonaceous fuel, means for proportioning said carbonaceous fuel in accordance with the Weight of other constituents, means for burning the feed and thereby evolving volatile oxides of carbon in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the carbon content in the feed comprising means connected with said passage for measuring the volume of flue gas, means connected with said passage for analyzing the flue gas for its content of said oxides, means for Weighing the sinter feed, computing means operatively connected with said volume-measuring means, with said analyzing means, and with said weighing means for determining the carbon content in the sinter feed, and means connecting said computing means and said proportioning means for adjusting the latter to eliminate differences between the carbon content as determined by said computing means and the desired carbon content.

10. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being carbonaceous fuel, means for proportioning said carbonaceous fuel in accordance with the weight of other constituents to produce a desired carbon content in the feed, means for burning the feed and thereby evolving volatile oxides of carbon in the resulting fiue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the carbon content in the feed more accurately than proportioning by weight alone comprising means connected with said passage for measuring the volume of line gas, means connected with said passage for analyzing the flue gas for its content of said oxides, means for weighing the sinter feed, computing means operatively connected with said volume-measuring means, with said analyzing means, and with said weighing means for determining the carbon content in the sinter feed, and a control computing means connected to said first named computing means and to said proportioning means for periodically adjusting the latter to eliminate any difference between the carbon content as determined by said first named computing means and the desired carbon content.

11. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being moisture, means for burning the feed and thereby evolving the moisture in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for'controlling the moisture content in the feed comprising means connected with said passage for measuring the moisture content in the feed through analysis of the flue gas, and means for adjusting said compounding means to bring the measured moisture content into conformity with the desired moisture content.

12. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being moisture, means for proportioning said moisture in accordance with the weight of other constituents, means for burning the feed and thereby evolving the moisture in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the moisture content in the feed comprising means connected with said passage for measuring the moisture content in the feed through analysis of the flue gas, and means connecting said measuring means and said prcportioning means to adjust the latter to bring the measured moisture content into conformity with the desired moisture content.

13. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being moisture, means for proportioning said moisture in accordance with the weight of other constituents, means for burning the feed and thereby evolving the moisture in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the moisture content in the feed comprising means connected with said passage for measuring the volume of flue gas, means connected with said passage for anlyzing the flue gas for its moisture content, means for Weighing the sinter feed, computing means operatively connected with said volume-measuring means, with said analyzing means, and with said weighing means for determining the moisture content in the sinter feed, and means connecting said computing means and said proportioning means for adjusting the latter to eliminate differences between the moisture content as determined by said computing means and the desired moisture content.

14-. In a sintering installation which includes means for compounding the constituents of a sinter feed, one of the constituents being moisture, means for proportioning said moisture in accordance with the weight of other constituents to produce a desired moisture content in the feed, means for burning the feed and thereby evolving the moisture in the resulting flue gas, and means forming a passage for said gas, the combination therewith of apparatus for controlling the moisture content in the feed more accurately than proportioning by weight alone comprising means connected with said passage for measuring the volume of flue gas, means connected with said passage for analyzing the flue gas for its moisture content, means for weighing the sinter feed, computing means operatively connected with said volume-measuring means, with said analyzing means, and with said weighing means for determining the moisture content in the sinter feed, and a control computing means connected to said first named computing means and to said proportioning means *for periodically adjusting the latter to eliminate any difference between the moisture content as determined by said first named computing means and the desired moisture content.

15. In a sintering process wherein individual constituents, at least one or" which is volatile-forming, are compounded to form a sinter feed andsaid feed is burned and said volatile-forming constituent evolved as volatile material in the resulting flue gas,'a method of controlling the content of said volatile-forming constituent comprising determining the content actually present in the feed through analysis of the flue gas, and adjusting the quantity compounded into the feed in accordance with the content thus determined.

16. In a sintering process wherein individual constitu cuts, atleast one of which is volatile-forming, are compounded to form a sinter feed, said volatile-forming constituent is proportioned in accordance with the weight of other constituents, and said feed is burned and said volatile-forming constituent evolved as volatile material in the resulting flue gas, a method of controlling the content or" said volatile-forming constituent more accurately than proportioning by weight alone comprising determining the content actually present in the feed through analysis of the flue gas, and periodically adjusting the proportion,

13 r compounded into the feed to eliminate difl'erences between the content thus determined and the desired content.

17. In a sintering process wherein individual constitucuts, at least one of which is volatile-forming, are compounded to form a sinter feed, said volatile-forming constituent is proportioned in accordance with the weight of other constituents, and said feed is burned and said volatile-forming constituent evolved as volatile material in the resulting flue gas, a method of controlling the content of said volatile-forming constituent more accurately than proportioning by weight alone comprising measuring the volume of flue gas, analyzing the flue gas for its content of said volatile material, weighing the sinter feed, computing the content of volatile-forming constituent in the feed from the volume measurement, the analysis of the flue gas and the weight of feed, and periodically changing the quantity of volatile-forming constituent proportioned into the feed to eliminate differences between the desired content and the computed content.

18. A method as defined in claim 17 in which the volatile-forming constituent is carbonaceous fuel.

19. A method as defined in claim 17 in which the volatile-forming constituent is moisture.

20. The method of determining the amount of moisture in a mix fed to sintering machines and the like which includes the steps of continuously determining the quantity of moisture required to be mixed with a continuously withdrawn sample of the ambient air to bring the moisture content of the ambient air sample up to the moisture content of a continuously withdrawn sample of the stack gases from the sintering machine, said quantity representing a measure of the amount of moisture in the stack gases coming from sources other than the ambient air, continuously weighing the mix supplied to the sintering machine, and determining the total moisture in said mix from the weight rate so determined and the said quantity of moisture in the stack gases from sources other than the ambient air.

21. The method of controlling the amount of moisture in a mix fed to sintering machines and the like which includes the steps of continuously determining the quantity of moisture required to be mixed with a continuously withdrawn sample of the ambient air to bring the moisture content of the ambient air sample up to the moisture content of a continuously withdrawn sample of the stack gases from the sintering machine, said quantity representing a measure of the amount of moisture in the stack gases coming from sources other than the ambient air, continuously weighing the mix supplied to the sintering machine, determining the total moisture in said mix from the weight rate so determined and the said quantity of moisture in the stack gases from sources other than the ambient air, continuously comparing said so-determined value of moisture content in the mix with a pre-selected set-point value, and adding water to the mix ahead of the weighing point to bring the moisture content of the mix at said weighing point to, and maintain it at, said set-point.

22. The method of maintaining a substantially constant moisture content in the mix supplied to sintering machines and the like, said sintering machine having mix heating apparatus and a stack through which gases from said mix heating apparatus are discharged, which includes continuously determining the amount of moisture removed from the mix during the sintering operation by continuously withdrawing a sample of the stack gas and measuring the amount of moisture added to the stack gases as a result of the sintering operation, adding water to the mix ahead of said mix heating apparatus, and automatically varying the amount of water so added to the mix in accordance with variations in the amount of moisture removed from the mix, the amount of water added being reduced when the quantity of moisture removed from the mix increases and being increased when the amount of moisture removed from the mix decreases.

23. Apparatus for automatically measuring the moisture content of a material mix supplied to sintering machines and the like including, means for continuously withdrawing a sample of stack gases from the sintering machine, means for continuously withdrawing a sample of ambient air from adjacent the sintering machine, means for determining a measure of the quantity of moisture in said stack gases that originated from sources other than the ambient air, means for continuously measuring quantity of mix supplied to the sintering machine, and means for continuously dividing said quantity of moisture from sources other than the ambient air by the quantity of material mix supplied to obtain a continuous value indicating the moisture content of the material mix supplied to the sintering machine or the like.

24. Apparatus for automatically measuring the moisture content of a material mix supplied to sintering machines and the like including, means for continuously withdrawing a sample of stack gases from the sintering machine, means for continuously withdrawing a sample of ambient air from adjacent the sintering machine, means for determining a measure of the quantity of moisture in said stack gases that originated from sources other than the ambient air, means for continuously measuring the the quantity of mix supplied to the sintering machine, means for continuously dividing said quantity of moisture from sources other than the ambient air by the quantity of material mix supplied to obtain a continuous value indicating the moisture content of the material mix supplied to a sintering machine or the like, controller means adapted to compare said value of the moisture content of the material mix to an adjustable set point, means for supplying water to said mix ahead of said means for continuously measuring the quantity of mix, controller means responsive to said value of the moisture content of the material mix, and means controlled by said controller means for varying the amount of water supplied to said mix whereby the moisture content in said material mix is maintained substantially at a predetermined value.

25. The method of determining the amount of moisture in a mix fed to sintering machines and the like which includes the steps of continuously heating said mix to drive out all moisture therefrom, conducting the moisture so driven out to a stack, continuously determining the ratio of the moisture in the stack gases from the sintering machine that comes from sources other than the ambient air to the total moisture in said stack gases, continuously measuring the rate of flow of the stack gases, continuously multiplying said rate by said ratio whereby a value is obtained that represents the quantity of moisture other than ambient air .moisture in the stack gases, continuously measuring the quantity of mix supplied to the sintering machine, and continuously determining, from said quantity of moisture other than ambient air moisture in the stack gases and said quantity of mix, a value representing the proportion of moisture in the mix.

26. The method of regulating the amount of moisture in a mix fed to sintering machines and the like which includes the steps of continuously heating said mix to drive out all moisture therefrom, continuously determining the ratio of the moisture in the stack gases from the sintering machine that comes from sources other than the ambient air'to the total moisture in said stack gases, continuously measuring the rate of flow of the stack gases, continuously multiplying said rate by said ratio whereby a value is obtained that represents the quantity of moisture other than ambient air moisture in the stack gases, continuously measuring the quantity of mix supplied to the sintering machine, continuously determining, from said quantity of moisture other than ambient air moisture in the stack gases and said quantity of mix, a value representing the proportion of moisture in the mix, continuously comparing said value representing the moisture in the mix with a preselected set-point value, and adding water to the mix ahead of the place at which said quantity of mix is measured to bring the moisture contained in the mix at said place to, and maintain it at, said set-point.

References Citesiin the file of this patent UNITED STATES PATENTS Franchot et a1 Sept. 29, 1925 Witz Oct. 5, 1926 Poole Ian. 25, 1927 Austin et a1 June 9, 1931 Lindemuth July 29, 1952 Harter Aug. 19, 1952 Hadady June 30, 1953 De Vaney et a1 Apr. 20, 1954 Sisco Mar. 27, 1956 Carney Feb. 5, 1957 OTHER REFERENCES Hubbell: Iron and Steel Engineer, August 1953, pages Johnson Nov. 12, 1946 10 5348- 

15. IN A SINTERING PROCESS WHEREIN INDIVIDUAL CONSTITUENTS, AT LEAST ONE OF WHICH IS VOLATILE-FORMING, ARE COMPOUNDED TO FORM A SINTER FEED, SAID VOLATILE-FORMING CONSAID VOLATILE-FORMING CONSTITUENT EVOLVED AS VOLATILE MATERIAL IN THE RESULTING FLUE GAS, A METHOD OF CONTROLLING THE CONTENT OF SAID VOLATILE-FORMING CONSTITUENT COMPRISING DETERMINING THE CONTENT ACTUALLY PRESENT IN THE FEED THROUGH ANALYSIS OF THE FLUE GAS, AND ADJUSTING THE QUANTITY COMPOUNDED INTO THE FEED IN ACCORDACE WITH THE CONTENT THUS DETERMINED. 